1. Field of the Invention
The present invention relates to a stimulable phosphor sheet having a stimulable phosphor layer and a cassette storing the stimulable phosphor sheet.
2. Description of the Related Art
There has been known a radiation image recording reproducing system using stimulable phosphor which stores a portion of energy of radiation (such as X-rays, a rays, rays, rays, electron rays, and ultraviolet rays) irradiated thereon and emits light in accordance with the energy stored therein upon exposure to excitation light such as visible light (Japanese Unexamined Patent Publication Nos. 55(1980)-12429, 56(1981)-11395, and 56(1981)-11397, for example). In such a system, radiation image information of a subject such as a human body is recorded on a stimulable phosphor sheet and the sheet is scanned with excitation light such as a laser beam to have the sheet emit light. The light is photoelectrically read to obtain an image signal, and a radiation image of the subject is output as a visible image on a recording medium such as a photosensitive material or on a display apparatus such as a CRT, based on the image signal.
As methods of photoelectrically reading the light, single-side reading and double-side reading are known. In single-side reading, an image signal is read only from one side of a stimulable phosphor sheet. In double-side reading, image signals are read respectively from each side of a stimulable phosphor sheet having a layer of stimulable phosphor. The layer is formed on a front side of a transparent base-material sheet comprising a transparent film or the like of 100xcx9c500 xcexcm thickness, for example. Radiation is irradiated from the side of the stimulable phosphor layer on the stimulable phosphor sheet to record radiation image information. The stimulable phosphor sheet is then scanned with excitation light from the side of the stimulable phosphor layer, and light emitted to both a front side (the side of the stimulable phosphor layer) and to a backside (the side of the transparent base material) of the stimulable phosphor sheet is read respectively by photoelectric reading means on the front side and the backside (see Japanese Unexamined Patent Publication No. 55(1980)-87970, for example). In double-side reading, by carrying out an addition process on signals obtained from both sides at pixels corresponding to each other, light collection efficiency improves and noise components are averaged. Therefore, an S/N ratio of a radiation image obtained in this manner can be improved.
In the radiation image recording reproducing system described above, photographing is carried out by using a stimulable phosphor sheet stored in a cassette having a flat shape. In the case where a photographed image is read, the cassette is set on an automatic reading apparatus. The reading apparatus automatically opens the cassette and takes out the stimulable phosphor sheet to carry out reading.
Different cassettes are used for single-side reading and for double-side reading. Therefore, the reading apparatus judges whether a stimulable phosphor sheet stored in a cassette is for single-side reading or for double-side reading, by reading a bar code on the cassette or on the stimulable phosphor sheet. In this manner, appropriate reading is carried out.
For example, if a cassette for double-side reading is set on an automatic reading apparatus, the reading apparatus reads a bar code of the cassette and recognizes that the cassette is for double-side reading. Assuming that a sheet in the cassette is for double-side reading, the reading apparatus then carries out addition processing on image signals read from both sides of the sheet by using a predetermined addition ratio.
However, a conventional cassette for single-side reading and a conventional cassette for double-side reading are substantially identical in appearance, and a stimulable phosphor sheet for single-side reading has substantially the same shape as a stimulable phosphor sheet for double-side reading. Therefore, a stimulable phosphor sheet for single-side reading can often be mistakenly stored in a cassette for double-side reading while a stimulable phosphor sheet for double-side reading can be stored in a cassette for single-side reading.
Furthermore, since the automatic reading apparatus described above is set to carry out the reading process on the premise that a combination of a cassette and a stimulable phosphor sheet is right, the reading apparatus carries out double-side reading by recognizing a bar code on a double-side reading cassette, even if a stimulable phosphor sheet for single-side reading is stored in the cassette by mistake. As a result, the reading apparatus outputs an image signal from the sheet after carrying out addition processing on image signals read from both sides. Since light is not detected from the backside of the stimulable phosphor sheet for single-side reading, no backside image signal is practically added. Therefore, an image represented by the image signal obtained as a result becomes extremely unclear.
Moreover, in the case of a stimulable phosphor sheet for double-side reading having a stimulable phosphor layer on a front side of a transparent base material, the front side is not easily distinguished from a backside thereof, since the base material is transparent. For example, when the sheet is stored in a cassette, the sheet can be mistakenly stored face down in the cassette, although it should be stored in such a manner that the front side of the sheet faces a front side of the cassette (the side which faces a radiation source at the time of photographing).
The reading apparatus scans the stimulable phosphor sheet from the front side, that is, from the side of the stimulable phosphor layer, assuming that the sheet for double-side reading is appropriately stored in the cassette. If the sheet for double-side reading is set face down in the cassette, the reading apparatus actually carries out the scan from the side of the transparent base material, which causes appropriate reading to become difficult due to the scanning via the transparent base material. Consequently, sharpness of an image obtained thereby degrades a great deal.
The present invention has been conceived based on consideration of the above problems. An object of the present invention is therefore to provide combinations of stimulable phosphor sheets and cassettes therefor, for avoiding a problem of erroneous combination of a stimulable phosphor sheet for double-side reading and a cassette for single-side reading and vice versa.
Another object of the present invention is to provide a combination of a stimulable phosphor sheet for double-side reading and a cassette therefor, for avoiding a problem of face down setting of the double-side reading stimulable phosphor sheet in the cassette.
Combinations of stimulable phosphor sheets and cassettes of the present invention are a combination of a double-side reading stimulable phosphor sheet enabling reading from both sides of the sheet and a cassette for double-side reading having a container area for containing said double-side reading stimulable phosphor sheet, and a combination of a single-side reading stimulable phosphor sheet enabling reading only from one side of the sheet and a cassette for single-side reading having a container area for containing the single-side reading stimulable phosphor sheet. The combinations of the present invention are characterized in that the double-side reading stimulable phosphor sheet has a shape different from the shape of the single-side reading stimulable phosphor sheet and a shape of the container area of the cassette for double-side reading prevents the single-side reading stimulable phosphor sheet from being contained in the cassette due to a difference in the shapes of the sheets.
As the shapes of the sheets and the container area of the cassette for double-side reading, the single-side reading sheet has an additional part not existing in a corresponding position in the double-side reading stimulable phosphor sheet, and the shape of the container area of the cassette for double-side reading prevents the single-side reading stimulable phosphor sheet from being contained in the cassette due to the additional part of the single-side reading stimulable phosphor sheet, for example.
The xe2x80x9ccorresponding position in the double-side reading stimulable phosphor sheetxe2x80x9d refers to a position in the double-side reading stimulable phosphor sheet in which the additional part exists in the single-side reading stimulable phosphor sheet.
Other combinations of stimulable phosphor sheets and cassettes of the present invention are a combination of a double-side reading stimulable phosphor sheet enabling reading from both sides of the sheet and a cassette for double-side reading having a container area for containing the double-side reading stimulable phosphor sheet and a combination of a single-side reading stimulable phosphor sheet enabling reading only from one side of the sheet and a cassette for single-side reading having a container area for containing the single-side reading stimulable phosphor sheet. The combinations of the present invention are characterized in that the double-side reading stimulable phosphor sheet has a shape different from a shape of the single-side reading stimulable phosphor sheet and a shape of the container area of the cassette for double-side reading prevents the single-side reading stimulable phosphor sheet from being contained in the cassette due to a difference in the shapes of the sheets while a shape of the container area of the cassette for single-side reading prevents the double-side reading stimulable phosphor sheet from being contained in the cassette due to the difference in the shapes of the sheets.
As the shapes of the single-side reading stimulable phosphor sheet and the container area of the cassette for double-side reading, the single-side reading sheet is formed to have an additional part not existing in a corresponding position in the double-side reading stimulable phosphor sheet, and the shape of the container area of the cassette for double-side reading prevents the single-side reading stimulable phosphor sheet from being contained in the cassette due to the additional part of the single-side reading stimulable phosphor sheet, for example. Meanwhile, as the shapes of the double-side reading stimulable phosphor sheet and the container of the cassette for single-side reading, the double-side reading sheet has an additional part not existing in a corresponding position in the single-side reading stimulable phosphor sheet, and the shape of the container area of the cassette for single-side reading prevents the double-side reading stimulable phosphor sheet from being contained in the cassette due to the additional part of the double-side reading stimulable phosphor sheet, for example.
As the additional parts, a thick additional part having more thickness or an additional plane part having a wider area may be used, for example.
In the combinations of the stimulable phosphor sheets and the cassettes, it is preferable for the double-side reading stimulable phosphor sheet to have different shapes when viewed from a front side and from a backside thereof while it is preferable for the shape of the container area of the cassette for double-side reading to prevent the double-side reading stimulable phosphor sheet from being contained in the cassette in a face down state, due to a difference in the shapes of the double-side reading stimulable phosphor sheet viewed from the front side and from the backside thereof.
Still other combinations of stimulable phosphor sheets and cassettes of the present invention are a combination of a double-side reading stimulable phosphor sheet enabling reading from both sides of the sheet and a cassette for double-side reading having a container area for containing the double-side reading stimulable phosphor sheet and a combination of a single-side reading stimulable phosphor sheet enabling reading only from one side of the sheet and a cassette for single-side reading having a container area for containing the single-side reading stimulable phosphor sheet. The combinations of the present invention are characterized in that either the double-side reading stimulable phosphor sheet or the single-side reading stimulable phosphor sheet has a colored part and the cassette for the sheet having the colored part has a colored part corresponding to the colored part of the sheet.
Yet other combinations of stimulable phosphor sheets and cassettes of the present invention are a combination of a double-side reading stimulable phosphor sheet enabling reading from both sides of the sheet and a cassette for double-side reading having a container area for containing the double-side reading stimulable phosphor sheet and a combination of a single-side reading stimulable phosphor sheet enabling reading only from one side of the sheet and a cassette for single-side reading having a container area for containing the single-side reading stimulable phosphor sheet. The combinations of the present invention are characterized in that both the double-side reading stimulable phosphor sheet and the single-side reading stimulable phosphor sheet have respective colored parts having different shapes or colors or in different positions and the cassettes to contain the respective sheets have respective colored parts corresponding to the colored parts of the corresponding sheets.
The colored part in the double-side reading stimulable phosphor sheet may be formed only on either a front side or a backside thereof so that the colored part in the cassette for double-side reading is formed on a material facing the side of the double-side reading sheet on which the colored part of the sheet is formed. Furthermore, the colored parts of the double-side reading stimulable phosphor sheet may be formed on both sides of the sheet in different shapes or colors or in different positions so that the colored parts of the cassette for double-side reading are formed on materials facing both the sides of the sheet, corresponding to the colored parts on both the sides of the sheet.
According to the combinations of the stimulable phosphor sheets and the cassettes of the present invention, the stimulable phosphor sheet for double-side reading has a different shape from the stimulable phosphor sheet for single-side reading, and the cassette for double-side reading has the shape disabling the sheet for single-side reading from being contained therein, due to the difference in the shapes of the sheets. Therefore, the cassette for double-side reading cannot contain the sheet for single-side reading, and a problem of erroneous setting of the stimulable phosphor sheet for single-side reading in the cassette for double-side reading can be securely avoided. In this manner, in appropriate reading of the stimulable phosphor sheet for single-side reading in the cassette for double side reading can be prevented from being carried out.
In the combinations of the stimulable phosphor sheets and the cassettes of the present invention, the stimulable phosphor sheet for double-side reading has a shape different from the shape of the stimulable phosphor sheet for single-side reading. In addition, each of the cassettes has the shape that disables the sheet of a different combination from being contained therein. Therefore, the sheet for single-side reading cannot be stored in the cassette for double-side reading, and vice versa. In this manner, erroneous sheet insertion in the cassette of the other combination can be prevented with certainty.
If the stimulable phosphor sheet for double-side reading has different shapes when viewed from the front side and the backside thereof, and if the cassette for double-side reading has the shape disabling the stimulable phosphor sheet for double-side reading from being contained therein in a face down state due to the shape difference, the stimulable phosphor sheet cannot be contained in the cassette face down. Therefore, the sheet is securely prevented from being contained face down in the cassette.
In the combinations of the stimulable phosphor sheets and the cassettes of the present invention, if either the stimulable phosphor sheet for single-side reading or the stimulable phosphor sheet for double-side reading has a colored part and if only the cassette for containing the sheet having the colored part has a colored part corresponding to the colored part of the sheet, the stimulable phosphor sheet having the colored part is set in the cassette having the colored part while the stimulable phosphor sheet not having the colored part is set in the cassette not having the colored part. In this manner, erroneous setting can be avoided.
Furthermore, in the combinations of the stimulable phosphor sheets and the cassettes of the present invention, both the stimulable phosphor sheets for double-side reading and single-side reading have the colored parts of different shapes or colors or in different positions, and the cassettes therefor have the respective colored parts corresponding to the colored parts of the sheets to be contained therein. Therefore, without distinction between the stimulable phosphor sheets, the stimulable phosphor sheets are simply contained in the respective cassettes having the colored parts corresponding to the colored parts thereof. In this manner, erroneous setting can be avoided.
If the colored part of the stimulable phosphor sheet for double-side reading is formed only on either the front side or the backside thereof, and if the colored part of the cassette for double-side reading is formed on the material facing the side of the sheet having the colored part thereon, the colored part of the sheet is simply matched with the colored part of the cassette at the time of setting the sheet in the cassette. In this manner, a problem of setting the sheet face down can be prevented.
Moreover, if the colored parts of the stimulable phosphor sheet for double-side reading are formed on both sides thereof in different shapes or colors or in different positions, and if the colored parts of the cassette for double-side reading are formed on the materials facing the respective sides of the sheet to correspond to the respective colored parts of the sheet, the colored parts of the sheet are simply matched with the colored parts of the cassette at the time of setting the sheet in the cassette. In this manner, the sheet can be prevented from being set face down.